This invention relates to methods and apparatus for excising mobile and non-mobile atheromatous plaque from the aortic wall and valve and also other arteries such as the carotid arteries and femoral arteries. The devices include an atherectomy catheter system for operation in the aorta, common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, vertebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery and all other arteries carrying oxygenated blood, and the catheter may optionally include blood filter means which enable the capture of plaque inadvertently dislodged during an atherectomy procedure.
The importance of the aorta as a source of emboli has only recently become apparent since the advent of transesophageal echocardiography (TEE). This technique has enabled physicians to visualize the aortic wall in great detail and to quantify atheromatous aortic plaque according to thickness, degree of intraluminal protrusion, and presence or absence of mobile components. See Katz et al., Journal of the American College of Cardiology 20:70-77 (1992), this and all other references cited herein are expressly incorporated by reference as if set forth herein in their entirety. Anecdotal reports linking embolic events to the presence of mobile aortic atheroma have lead to large-scale studies aimed at establishing the exact relationship between aortic atheromatosis and cerebral embolization. See Flory, American Journal of Pathology 21:549-565 (1945); Beal et al., Neurology 31:860-865 (1981); Soloway et al., Archives of Neurology 11:657-667 (1973); Russell et al., Stroke 22:253-258 (1991); and Tunick et al., Annals of Internal Medicine 114:391-392 (1991).
In 1992, and again in 1994, Amarenco disclosed an unequivocal association between embolic stroke and TEE-detected aortic plaque, especially in the presence of mobile plaque. See Amarenco et al., Stroke 23:1005-1009 (1992); and Amarenco et al., New England Journal of Medicine 331:1474-1479 (1994). Amarenco performed a prospective, case-control study of the frequency and thickness of atherosclerotic plaques in the ascending aorta and proximal arch in 250 patients with stroke and in 250 controls. Amarenco found protruding plaque (4 mm) in 14.4% of patients with stroke but only 2% of control. Plaques of all thickness were associated with stroke, but the association was strongest for plaques more than 4 mm in thickness. Protruding plaque was present in 28.2% of 78 patients with stroke of unknown cause, compared with 8.1% of 172 patients with stroke of known or likely causes. Furthermore, mobile plaque was present in 7.7% of patients with stroke of unknown cause, compared with only 0.6% of patients with stroke of known cause. The association between protruding atheroma and stroke was strongest for ascending aorta and proximal arch, but weaker for the distal arch and descending aortic disease.
Ulcerated aortic plaque, the pathologic correlate of TEE-detected mobile plaque, was present in autopsies of 26% of 239 patients with cerebrovascular disease as compared with 5% of 261 patients with other neurologic diseases. The prevalence of ulcerated arch lesions was 61% among 28 patients with no known causes of brain infarction, as compared with 22% among 155 patients with a known cause of infarction. See Amarenco et al., New England Journal of Medicine 326:221-225 (1992).
Amarenco and others showed prospectively (following patients for two years) a strong correlation between mobile plaque and embolic stroke or emboli to the legs and/or kidneys. In an attempt to investigate the value of aortic atheroma in predicting future vascular events, Tunick followed 42 patients with TEE-detected protruding atheroma and an equal number of controls for up to two years. See Tunick et al., Journal of the American College of Cardiology 23:1085-1090 (1994). Fourteen (33%) patients with protruding plaque had 19 embolic events, as compared with 3 out of 42 (7%) controls. These observations have been independently confirmed by a number of other recent studies on risk factors of embolic stroke. See Tunick et al., American Heart Journal 120:658-660 (1990), Karalis et al., Journal of the American College of Cardiology 17:73-78 (1991), Tunick et al., Annals of Internal Medicine 115:423-427 (1991), Tunick et al., American Heart Journal 124:239-241 (1992), Horowitz et al., Neurology 42:1602-1604 (1992), Toyoda et al., Stroke 23:1056-1061 (1992), Nihoyannopoulos et al., American Journal of Cardiology 71:1208-1212 (1993), Davila-Roman et al., Stroke 25:2010-2016 (1994), and the French Study of Aortic Plaques in Stroke Group, New England Journal of Medicine 334(19):1216-1221 (1996).
The danger of embolic stroke from atheroma present in the aorta, especially of mobile plaque, has been shown in patients undergoing cardiac surgery, and this effect is due to mechanical manipulations performed on the aorta during cardiac surgery. See Hartman et al., Anesthesia Analgesia 1996 (in press), Gold et al., Journal of Thoracic Cardiovascular Surgery 110:1302-1314 (1995), Marshall et al., Annals of Thoracic Surgery 48:339-344 (1989), Katz et al., Journal of American College of Cardiology 20:70-77 (1992); and Hosoda et al., Journal of Cardiovascular Surgery 32:301-306 (1991). In fact, among patients undergoing coronary bypass surgery, aortic atheromatosis has emerged as the single most important factor in perioperative neurologic morbidity. See Tunick et al., Annals of Internal Medicine 114:391-392 (1991); Karalis et al., Journal of the American College of Cardiology 17:73-78 (1991); Marschall et al., Journal of Cardiothoracic Vascular Anesthesia 8:5-13 (1994); Blauth et al., Journal of Thoracic Cardiovascular Surgery 103:1104-1112 (1992); Wareing et al., Journal of Thoracic Cardiovascular Surgery 103:453-462 (1992); Ribakove et al., Annals of Thoracic Surgery 53:758-763 (1992); Brillman, Neurologic Clinics 11:475-495 (1993); and Amarenco et al., Stroke 23:1005-1009 (1992). As the number of elderly patients undergoing bypass surgery has increased, the decline in overall mortality and cardiac morbidity achieved by improvements in surgical and anesthetic techniques has been largely obscured by increasing neurologic complication rates. See Loop et al., Cleveland Clinical Journal of Medicine 55:23-24 (1988); Hill et al., Annals of Thoracic Surgery 7:409-419 (1969); Gardner et al., Annals of Thoracic Surgery 40:574-581 (1985); and Cosgrove et al., Journal of Thoracic Cardiovascular Surgery 88:673-684 (1984). Aortic atheroma increases sharply with age, from 20% in the fifth decade at necropsy to 80% over the age of 75 years, and stroke rate increases from 1% in patients 51 to 60 years to 7% or more in those over 75 years. See Fisher et al., Journal of Neuropathology and Experimental Neurology 24:455-476 (1965); Amarenco et al., Stroke 23:1005-1009 (1992); Marschall et al., Journal of Cardiothoracic Vascular Anesthesia 8:5-13 (1994); Blauth et al., Journal of Thoracic Cardiovascular Surgery 103:1104-1112 (1992); Wareing et al., Annals of Thoracic Surgery 55:1400-1408 (1993); and Davila-Roman et al., Circulation 84 III-47-III-53, 1991 [suppl 3]; Wareing et al., Journal of Thoracic Cardiovascular Surgery 103:453-462 (1992); Gardner et al., Annals of Thoracic Surgery 40:574-581 (1985); Cosgrove et al., Journal of Thoracic Cardiovascular Surgery 88:673-684 (1984); Davila-Roman et al., Stroke 25:2010-2016 (1994); Bar-El et al., Journal of Thoracic Cardiovascular Surgery 104:469-474 (1992); and Saloman et al., Journal of Thoracic Cardiovascular Surgery 101:209-218 (1991). Among patients dying after coronary bypass surgery, evidence of atheroembolism was present in only 4.5% in 1982, and in as many as 48% in 1989. See Wareing et al., Journal of Thoracic Cardiovascular Surgery 103:453-462 (1992).
Embolization from the aorta, particularly to the brain, is therefore a major problem, and emboli from this source can lead to stroke, myocardial infarction, kidney infarcts, and peripheral emboli in other organs. There is a presently unfulfilled need for an atherectomy device for use in the aorta to prevent the above-identified disorders arising from embolization. Moreover, it will be understood that fixed plaque exists both in the aorta and in the carotid arteries, which may also lead to stroke by embolization. Thus, there is a presently unfulfilled need for an atherectomy device for use in both aorta and carotid arteries to prevent embolization from such fixed plaque. Another site at which fixed plaque may build up is in the iliac and femoral arteries. Claudication may result from inadequate blood flow in or embolization to the iliac and femoral arteries. A need therefore exists for an atherectomy device for use in the iliac and femoral arteries to prevent claudication by increasing blood flow and also preventing embolization to the lower extremities.
The coronary arteries, by contrast, present entirely different considerations with respect to atherectomy. In the coronary arteries, myocardial ischemia or infarction is typically caused by a reduction in blood flow by reason of the build up of atheroma causing stenosis, rather than dislodgment of embolic material from such plaques. Atherectomy in the coronary arteries therefore prevents myocardial infarction by increasing blood flow due to an enlargement of the luminal diameter on removal of stenosis. Accordingly, there exists an extensive body of literature that addresses the use of atherectomy in relation to stenosis as applied in the coronary arteries. For example, Fischell, U.S. Pat. No. 5,409,454, discloses a retrograde cutting atherectomy catheter designed to perform atherectomy on an eccentric stenosis by cutting plaque from one part of an arterial wall while shielding a normal portion of the arterial wall from being cut. Fischell, U.S. Pat. No. 4,898,575, discloses a tunneling catheter system that rides on a guidewire for percutaneous transluminal atherectomy. Rydell, U.S. Pat. No. 4,857,045, discloses an atherectomy catheter having a motor driven cutting member and capabilities for flushing the treatment site and aspirating a flushing liquid so as to remove debris loosened during a procedure. Moreover, Yock, U.S. Pat. Nos. 4,794,931, 5,000,185, and 5,313,949, disclose catheters having a cutting member for atherectomy and an ultrasound transducer which enables ultrasonography in combination with atherectomy. Meanwhile, Jang et al., U.S. Pat. No. 5,507,292, discusses abrasive atherectomy in combination with ultrasound imaging. The patent and medical literature is replete with additional disclosures of atherectomy as applied to the coronary arteries, and this subject will not be further discussed here for the sake of brevity. The interested reader is referred to the following disclosures for more information: Farr, U.S. Pat. Nos. 4,950,277, 4,986,807, 5,019,088, Shiber, U.S. Pat. Nos. 4,894,051, 4,957,482, 4,979,939, 5,007,896, 5,024,651, 5,135,531, Summers, U.S. Pat. No. 5,087,265, Plassche et al., U.S. Pat. No. 5,318,576, Belknap, U.S. Pat. No. 5,366,464, Jang et al., U.S. Pat. No. 5,402,790, Mazur et al., Catherization and Cardiovascular Diagnosis 31:79-84 (1994), Fischell et al., U.S. Pat. Nos. 4,886,061, 5,100,425. It will be appreciated that coronary artery atherectomy devices do not prevent embolization, but this does not appear to be a major consequence during this procedure.
Insofar as we are aware, however, there has been no disclosure of an atherectomy catheter adapted for trapping and removing mobile plaque or fixed plaque in the aorta, carotid, or femoral arteries and having an ability to remove embolic material generated during the procedure. Accordingly, a need exists for an arterial atherectomy catheter having an ability to entrap and/or snare, and thereafter remove aortic, carotid, and femoral artery plaque without generating atheromatous embolization.
We have discovered that mobile aortic plaque present in the aorta is a major contributor to the occurrence and recurrence of ischemic stroke. Mobile aortic plaque is a term that refers to vascular deposits comprising a solidified base and a floppy projection attached to the base. The floppy projection is most easily dislodged by normal pulsating blood flow or by an invasive procedure such as angiography, angioplasty, stenting, or cardiac surgery, and may produce embolic material. The build up of mobile aortic plaque, as well as the number and extent of the floppy projections, increases with age and therefore the risk of ischemic stroke, myocardial infarction, and systemic emboli due to release of a floppy projection into the blood stream also increases with age.
Atherectomy of the aorta can prevent each of the above diseases from occurring, but can also cause these diseases unless the atherectomy device is specially designed to enter the aorta without scraping against plaque, or includes a filter which is inserted and deployed to capture embolic material dislodged during the procedure. While reduction in blood flow is typically not a problem in the aorta due to the large diameter of this vessel, in the carotid arteries, fixed plaque poses a risk of stroke by embolization, and presents an additional threat of reducing blood flow by occluding the vessel lumen. Thus, atherectomy in the carotid arteries can prevent stroke by either increasing blood flow or reducing the potential for formation of embolic material. However, carotid atherectomy also poses a risk in that the atherectomy instrument can dislodge plaque, and thereby cause stroke by embolization. Fixed plaque is also present in the descending aorta and its dislodgment may cause kidney infarcts or ischemia to other end-organs. Fixed plaque is also present in the iliac arteries and femoral arteries, which in turn may cause peripheral leg ischemia either through distal embolization of atheromatous material or through in situ stenosis of the diseased blood vessel (narrowing of luminal diameter). Femoral artery atherectomy prevents appendicular claudication caused by plaque occluding the lumen of the femoral artery; atherectomy, however, results in distal embolization of atheromatous material, which in turn may cause limb ischemia.
The present invention relates to arterial medical devices that are adapted to remove mobile aortic plaque without generating embolic material, which can create a risk of ischemic stroke. As discussed above, numerous medical devices have been proposed for atherectomy in the coronary arteries. However, these devices do not reduce the risk of embolization associated with such procedures; the catheters themselves are likely to dislodge plaque material during positioning, and these devices do not include structures to prevent escape of embolic material. By contrast, the devices of the present invention generally include an arterial atherectomy catheter having suction means or a mechanical trapping device that acts to draw in and secure a mobile plaque. Mobile plaque, without trapping, presents a target difficult to maintain in contact. The atherectomy devices herein further include a cutting member to excise plaque once captured by the device, and optionally include a blood filter mechanism. Moreover, the invention includes methods of using the devices to remove plaque from the aortic wall, aortic valve, carotid arteries, and/or femoral artery. Those devices, which include a filter mechanism, will remove embolic material from blood, and thereby prevent occurrence of ischemic stroke, myocardial infarction, or systemic embolus. Embolic material in this setting is any constituent of blood, or atheromatous material and superimposed thrombus, which may cause complications in the body if allowed to travel freely in the blood stream. This matter includes, but is not limited to, atheromatous fragments, fat, platelets, fibrin, clots, or gaseous material.
In one embodiment, the medical device comprises an arterial catheter system which includes a flexible elongate member or catheter having an outer surface, a distal region adapted to enter an artery, and a proximal region which extends from a patient""s vessel and permits control outside the patient""s body by a physician. At the distal region of the catheter is provided an atherectomy assembly which includes an excising member, e.g., a cutting blade, abrasive member, wire cutter, jaws, claws, pincher, snare, etc., and a trapping mechanism which, in certain embodiments, comprises an open-ended tubular member which extends to the proximal region of the catheter and is attached to a vacuum source. In other embodiments, the trapping mechanism comprises a snare, adjustable orifice, basket, grabber, opening in a tube, etc. The trapping and cutting of plaque may occur simultaneously or sequentially in either order. The atherectomy assembly may optionally further include means for intravascular imaging, e.g., an ultrasonic transducer, which means are filly described in the art and will not be further discussed here.
The arterial catheter system may also include a filtration mesh, typically disposed circumferentially about the distal region of the catheter. Devices for use in the aorta and femoral artery will typically have the filtration mesh proximal to the atherectomy assembly, whereas the catheter for carotid artery atherectomy will have the filtration mesh distal to the atherectomy assembly, so that in all cases filtration occurs downstream of atherectomy. The filter will typically include a continuous mesh having a first edge which is closely associated with the outer surface of the catheter and a second edge attached to an expansion mechanism which is expandable between a contracted condition and an enlarged condition. The construction and use of expansion means and associated filter mesh on an arterial blood cannula have been thoroughly discussed in our earlier applications including Barbut et al., U.S. application Ser. No. 08/553,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr. 30, 1996, and Barbut et al., U.S. application Ser. No. 08/645,762, filed May 14, 1996, and the contents of each of these prior applications are incorporated herein by reference in their entirety. It will be understood that the design and use of a filter mesh and associated expansion means as discussed in these applications is fully applicable to the use of such filter and expansion means on an arterial catheter system as disclosed herein. Moreover, it will be understood that the filter mesh need not be disposed circumferentially about the catheter, but may be arranged on one side, or distal to the distal end of the catheter. These other configurations are possible so long as the filter may be expanded to cover substantially the entire vessel lumen so that substantially all blood flowing downstream is filtered.
The methods of the present invention include protecting a patient from embolization during an atherectomy procedure to remove plaque from the aorta (aortic wall, aortic valve, or aortic root), common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, vertebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery and all other arteries carry oxygenated blood. The physician will typically determine the presence and location of mobile plaque using one or more of a number of visualization techniques including transesophageal echocardiography (TEE), epiaortic ultrasonography. Another visualization technique, intravascular ultrasound, may also be useful in evaluating the presence and location of mobile plaque in the aorta, carotid, and femoral artery. Unlike the other techniques mentioned, intravascular ultrasound visualizes the blood vessel from its inside. Transcranial Doppler ultrasonography may be used for cerebral monitoring of emboli during the atherectomy procedure.
In use, the distal end of the arterial catheter is inserted and deployed through an incision in the femoral or brachial artery in a manner widely used for deployment of coronary artery angioplasty, atherectomy, and ultrasonography catheters. Thus, certain procedures are so-called de novo catheterizations performed for the purpose of removing plaque from the aorta, common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, vertebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery and all other arteries carry oxygenated blood. In other cases, the present invention will be an add-on procedure at the end of, or possibly before, a cardiac catheterization procedure. In either case, the procedure will typically be conducted in a standard xe2x80x9ccatheterization laboratoryxe2x80x9d rather than an operating room, although use in an operating room is an option.
The distal region of the catheter is advanced within the femoral or brachial artery until the distal end reaches a region of interest in the aorta, carotid, or femoral artery (a region having plaque that is to be removed). Advancement of the catheter tip may be assisted by X-ray fluoroscopy, and the distal region of the catheter may include one or more fluoroscopic markers to enable such visualization. Advancement may also be assisted by IVUS or TEE, or by a conventional guidewire and/or a guiding catheter, both of which are known in the art for coronary catheterization. Typically, it is difficult to navigate the aortic arch without some assistance from visualization, mechanical guidance, or both. Where associated filtration is to be used (a feature which is optional), the expansion means, including associated mesh, is inflated or deployed to expand and thereby achieve contact if need be with the inner wall of the artery. Once the filtration means are in place and deployed, a trapping mechanism (suction, claws, jaws, or an orifice with a mouth having an adjustable opening) is positioned in close proximity to the plaque of interest, and thereafter activated in order to draw in and secure the plaque. In the absence of such a grabbing mechanism, the plaque would present a moving target that is difficult to cut with any degree of accuracy, and could embolize by reason of contact with the medical device.
The plaque is securely held by the atherectomy assembly, and a cutting mechanism is deployed to remove or excise the plaque or a portion thereof. For atherectomy of mobile aortic plaque, it will be understood that before, during and after cutting, the floppy projection is typically held secure by the atherectomy assembly and therefore does not itself present a risk of release to form an embolus. In certain embodiments, grabbing and cutting of plaque will be simultaneously conducted, while in other embodiments, these steps are sequential and in either order. However, it is desirable to have an associated filter deployed downstream of the atherectomy assembly because the process of immobilizing and cutting plaque material may cause dislodgment of embolic material from the region of interest in the artery.
After the mobile plaque is excised and retained in the atherectomy device, the expansion means and filtration system, if used, are contracted by deflating or collapsing to resume a small shape in close contact with the outer surface of the catheter. The catheter, with captured embolic material in the atherectomy and optionally in the filtration system, is then withdrawn from the artery of interest and back into the femoral artery where it is ultimately removed from the patient""s body.